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| author | Wei-Ning Huang <w@byzantine-lab.io> | 2019-06-26 10:56:22 +0800 |
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| committer | Wei-Ning Huang <w@byzantine-lab.io> | 2019-09-17 16:53:55 +0800 |
| commit | 8948709eca6d688401b3d11e6abe1d5412e60d2a (patch) | |
| tree | 1f11718794677efe0cd11ad1d885ea1477d357c6 | |
| download | tangerine-random-lib-8948709eca6d688401b3d11e6abe1d5412e60d2a.tar.gz tangerine-random-lib-8948709eca6d688401b3d11e6abe1d5412e60d2a.tar.zst tangerine-random-lib-8948709eca6d688401b3d11e6abe1d5412e60d2a.zip | |
Initial commit
| -rw-r--r-- | README.md | 37 | ||||
| -rw-r--r-- | RandomLib.sol | 13 |
2 files changed, 50 insertions, 0 deletions
diff --git a/README.md b/README.md new file mode 100644 index 0000000..1c56a9f --- /dev/null +++ b/README.md @@ -0,0 +1,37 @@ +# Tangerine Network RNG Library + +## Introduction + +Tangerine Network provides on-chain randomness through a precompiled contract. +Using a precompiled contract instead of introducing a new OP code ensures that +we are compatible with EVM, and eliminates the need to maintain a separate +toolchain. + +The precompiled contract is located at +`0xc327ff1025c5b3d2deb5e3f0f161b3f7e557579a`, which is the first 20 bytes of +`Keccak256Hash("Tangerine Network Random")`. The gas cost for each invocation is 64. + +To use the random library, simply include the library file then call `Random.rand()` to get the random number. + +## Example + +``` +import "github.com/tangerine-network/random-lib/RandomLib.sol"; + +contract UseRandom { + event Win(); + event Lose(); + + function readRand() public view returns (uint256) { + return Random.rand(); + } + + function bet() public { + if (Random.rand() % 100 >= 50) { + emit Win(); + } else { + emit Lose(); + } + } +} +``` diff --git a/RandomLib.sol b/RandomLib.sol new file mode 100644 index 0000000..228c804 --- /dev/null +++ b/RandomLib.sol @@ -0,0 +1,13 @@ +pragma solidity >= 0.5.0; + +library Random { + function rand() internal view returns (uint256) { + uint256[1] memory m; + assembly { + if iszero(staticcall(not(0), 0xC327fF1025c5B3D2deb5e3F0f161B3f7E557579a, 0, 0x0, m, 0x20)) { + revert(0, 0) + } + } + return m[0]; + } +} |